Internal combustion engines, and diesel engines particularly, often include an after-treatment system for treating exhaust gas from the engine. The after-treatment system uses an oxidation catalyst to heat the exhaust gas to a desired temperature to burn soot from the exhaust gas. The oxidation catalyst oxidizes unburned hydrocarbons in the exhaust gas to produce heat. The unburned hydrocarbons are injected into the exhaust gas through either a late in-cylinder injection process or an external post cylinder injection process.
In order for the oxidation catalyst to oxidize the unburned hydrocarbons, the oxidation catalyst must be heated to a light-off temperature of the oxidation catalyst. During low ambient air temperature conditions or at low exhaust flow conditions, heating the oxidation catalyst to the light-off temperature becomes difficult.